macarena

RESEARCHNOTE

BiofilmformationinAcinetobacter

baumannii:associatedfeaturesandclinical

implications

ı

´

guez-Ban

˜o1,ı

´2,2,

´

ndez-Cuenca3,os4,

´

n4,l3,ı

´

nez-

Martı

´

nez5,ry6,6,

2andtheSpanishGroupfortheStudy

ofNosocomialInfections(GEIH)

1Seccio

´

ndeEnfermedadesInfecciosas,3Servicio

deMicrobiologı

´

a,HospitalUniversitarioVirgen

Macarena,Sevilla,2ServiciodeMicrobiologı

´

a,

HospitalClinic,Barcelona,4Serviciode

EnfermedadesInfecciosas,HospitalUniversi-

tarioVirgendelRocı

´

o,Sevilla,5Serviciode

Microbiologı

´

a,HospitalUniversitarioMarque

´

s

deValdecilla,Santander,Spainand

6DepartmentofMicrobiology,MiamiUniversity,

Oxford,OH,USA

ABSTRACT

Biofilmformationin92unrelatedstrainsof

Acinetobacterbaumanniiisolatedinamulticentre

cohortstudywasinvestigatedusingamicrotitre

-six(63%)isolatesformed

biofisolateswerelessfrequentlyresis-

tanttoimipenemorciprofloxacinthanwerenon-

biofilm-formingisolates(25%vs.47%,p0.04;and

66%vs.94%,p0.004,respectively).Allcatheter-

relatedurinaryorbloodstreaminfectionsandthe

solecaofshunt-relatedmeningitiswerecaud

bybiofiariateanalysis

revealedthattreatmentinanintensivecareunit,

ciprofloxacinresistanceandisolationfromarespi-

ratorysamplewereassociatedwithnon-biofilm-

formingisolates,whilepreviousaminoglycoside

uwasassociatedwithbiofilm-formingisolates.

KeywordsAcinetobacterbaumannii,biofilmformation,

ciprofloxacinresistance,imipenemresistance,infec-

tions,risk-factors

OriginalSubmission:3June2007;RevidSubmis-

sion:5August2007;Accepted:14October2007

ClinMicrobiolInfect2008;14:276–278

10.1111/j.1469-0691.2007.01916.x

Acinetobacterbaumanniiisasignificantworldwide

nosocomialpathogenwithaparticularabilityto

developantimicrobialresistanceandcaunoso-

comialoutbreaksofinfection[1].Thisorganism

frequentlycausinfectionsassociatedwithmed-

icaldevices,e.g.,vascularcatheters,cerebrospinal

fluidshuntsorFoleycatheters[1–3].Biofilm

formationisawell-knownpathogenicmechanism

insuchinfections[4].Inaddition,theenviron-

mentalsurvivalofsomemicroorganismsmaybe

facilitatedbybiofilmformationonabioticsur-

isknownconcerningbiofilmforma-

nii[5–8].Therefore,theprent

studyinvestigatedthefrequencyofbiofilmfor-

mationandtheassociatedclinicalcorrelationsand

variablesfor92clonallyunrelatedisolateslected

niicollected

duringtheGEIH-Ab2000project[2],whichwasa

multicentreprospectivecohortstudyperformed

hodsandgeneral

clinical,epidemiologicalandmicrobiological

resultsofthisstudyhavebeenreportedindetail

elwhere[2,9,10].Forthepurpooftheprent

analysis,ifanisolateincludedinthisstudywas

clonallyrelatedtoatleastoneotherisolatefrom

theoriginalcollection,itwasconsideredtobe

epidemic[2].Thestudywasapprovedbythelocal

ethicscommitteesoftheparticipatinghospitals.

BiofilmformationwasdeterminedintheHos-

pitalClinic,Barcelona,Spain,usinganovernight

culture,diluted1:100infreshLuria–Bertonibroth

in96-wellplatesandincubatedwithoutshakingat

37°96wells,fourwereleft

-

filmwasstainedwithcrystalviolet1%w⁄vand

quantifiedat570nmaftersolubilisationwith

ethanol–erimentwasperformed

eswere

classifiedasbiofilm-formingiftheyyieldedOD

570

valuesthatwereatleasttwicethoofthenegative

isolatewasclearlypositivefor

biofilmformationintheassayandtheduplicate

assaywasborderline,theisolatewasconsideredto

bebiofiisolatewasclearly

positiveinthefirstassayandtheduplicateassay

wasclearlynegative,theisolatewasconsideredto

tibility

toantimicrobialagentswasdeterminedbymicro-

dilutionaccordingtoCLSIrecommendations[11].

Theepidemiologicalandclinicalfeatures

ofpatientscolonidorinfectedwithbiofilm-

Correspondingauthorandreprintrequests:ı

´

guez-Ban

˜

o,

Seccio

´

ndeEnfermedadesInfecciosas,HospitalUniversitario

VirgenMacarena,AvdaDrFedriani3,41009Sevilla,Spain

E-mail:************

Ó2008TheAuthors

JournalCompilationÓ2008EuropeanSocietyofClinicalMicrobiologyandInfectiousDias

formingandnon-biofinii

uousvariables

werecomparedusingtheMann–

WhitneyU-testandcategoricalvariableswere

comparedusingthechi-squaretest(Fisher’xact

test,ifrequired).Multivariateanalysiswas

performedbylogisticregressionanalysis.

StatisticalanalyswereperformedusingSPSS

v.12.0(SPSSInc.,Chicago,IL,USA).

Ofthe92isolatesstudied,56(63%)formed

biofilminvitro,33(36%)didnotformbiofilm,

andthree(3%),89

isolateswereudinthefigh

onereprentativeisolateofeachpuld-fieldgel

electrophoresistypewasinitiallyanalyd,the

resultsforbiofilmformationalwaysagreedwith

thereprentativeisolatewhenotherisolates

belongingtothesamepuld-fieldgelelectro-

phoresistypefromtheoriginalcollection(‘epi-

demicstrains’)film-forming

isolateswerelessfrequentlyimipenem-resistant

(25%vs.47%,p0.04),ciprofloxacin-resistant

(66%vs.94%,p0.004)andepidemic(31%vs.

53%,p0.04)thanwerenon-biofilm-formingiso-

ificantdifferencesinsusceptibility

todoxycycline(65%vs.60%),ceftazidime(73%

vs.83%),sulbactam(39%vs.27%),gentamicin

(80%vs.77%),tobramycin(76%vs.73%)or

rifampicin(0vs.3%)wereobrved(p>0.1).

Completeepidemiologicalandclinicaldata

wereavailablefor78patientsandwereincluded

intheanalysisoffactorsassociatedwithbiofilm

iateanalysareshownin

(95%CI)forthevariableslected

inmultivariateanalysiswere:treatmentinan

intensivecareunit,0.1(0.004–0.8);respiratory

tractsample,0.2(0.005–0.4);ciprofloxacinresis-

tance,0.06(0.009–0.4);andpreviousreceiptof

aminoglycosides,13.1(2.3–74.9).WhenCDCcri-

teriawereud[12],thefrequenciesofinfection

caudbybiofilm-formingandnon-biofilm-form-

ingisolatesweresimilar(20⁄49(41%)vs.13⁄29

(45%),p0.1).Typesofinfectionsareshownin

ionscaudbynon-biofilm-forming

isolatesshowedanon-significanttrendtoward

theprenceofpsisandahighermortalityrate

whencomparedwithinfectionscaudbybio-

film-formingisolates(92%vs.70%,p0.1,and

23%vs.14%,p0.6,respectively).

Thereisverylimitedinformationconcerning

the

nii

toformbiofilm[5–7].In

nii,

Sechietal.[8]foundthat16(80%)of20isolates

formedbiofilm,perhapsbecauofadominant

rentstudy,63%of

niiclinicalisolates

formedbiofistingly,allclonallyrelated

isolatessharedeitheranabilityoraninabilityto

formabiofilm,whichsuggeststhatthisisaclone-

specificfeatureandthatitxpressiondoesnot

varysubstantiallyunderdifferentconditions;

however,furtherstudiesareneededtoinvestigate

thishypothesis.

iateanalysisoffactorsassociatedwith

biofilm-formingisolatesofAcinetobacterbaumannii(data

expresdasapercentageofcasunlessotherwi

specified)

Biofilm-

forming

(n=49)

Non-biofilm-

forming

(n=29)OR(95%CI)pvaluea

Meanage,years(SD)b55(21)62(14)–0.08c

Malegender72780.7(0.2–2.0)0.5

Underlyingdia

Non-fatal7462–0.5

Ultimatelyfatal2432

Rapidlyfatal46

Diabetesmellitus10220.4(0.1–1.4)0.1

Neoplasia17280.5(0.1–1.5)0.2

Chronicpulmonary

dia

15280.5(0.1–1.5)0.2

ICUtreatment26530.3(0.1–0.7)0.01

Meandaysofhospital

stay(SD)

29(37)22(25)–0.3c

Centralvenouscatheter58610.8(0.3–2.2)0.7

Mechanicalventilation44520.7(0.2–1.8)0.4

Urinarycatheter77770.9(0.3–2.8)0.9

Previousantimicrobial

agents

86841.3(0.3–4.8)0.7

Aminoglycosides43203.0(0.9–10.3)0.06

Fluoroquinolones21102.4(0.5–12.3)0.2

Cephalosporins46272.3(0.8–6.2)0.09

Carbapenems13170.7(0.1–3.2)0.1

Typeofsample

Respiratorytract25530.3(0.1–0.8)0.01

Blood100–0.07d

Urine32143.0(0.9–10.1)0.06

Wound27270.9(0.3–3.0)0.8

Others660.9(0.1–8.1)0.8d

ICU,intensivecareunit;SD,standarddeviation.

aChi-squaretestexceptwherespecified.

bTherewereonlythreepaediatricpatients,allofwhomyieldedabiofilm-forming

isolate.

cMann–WhitneyU-test.

dFisher’xacttest.

finfectionscaudbybiofilm-forming

andnon-biofilm-formingisolatesofAcinetobacterbaumannii

(dataexpresdasabsolutenumbersofinfections)

Biofilm-forming

(n=20)

Non-biofilm

forming(n=13)

IVcatheter-relatedinfection30

Foley-relatedUTI60

CSFshuntinfection10

VArespiratorytractinfection58

Non-VArespiratorytractinfection10

Skinandsoft-tissueinfection45

IV,intravascular;UTI,urinarytractinfection;CSF,cerebrospinalfluid;VA,

ventilator-associated.

RearchNotes277

Ó2008TheAuthors

JournalCompilationÓ2008EuropeanSocietyofClinicalMicrobiologyandInfectiousDias

Althoughlimitedbythelownumberofcas,

theprentresultssuggestthatbiofilmplaysa

roleinthepathogenesisofsomedevice-associated

niiinfections(e.g.,thoinvolving

Foleycatheters,venouscathetersandcerebrospi-

nalfluidshunts);incontrast,ventilator-associated

pneumoniawasnotcaudpredominantlyby

biofiesultssuggest

thehypothesisthatinfectionscaudbybiofilm-

formingisolatesmightbeassociatedwitha

diminishedfrequencyofsystemicresponor

mortality;however,thisassociationwasnot

statisticallysignificantandfurtherstudieswould

benecessarytoinvestigatethispossibility.

Biofilm-formingisolateswerelessfrequently

resistanttoimipenemandciprofloxacin,and

bleexplana-

tionisthatbiofilm-formingisolatesarenotas

dependentastheirnon-biofilm-formingcounter-

partsonantimicrobialresistanceandepidemic

characteristicstosurviveinthehospitalenviron-

tal.[8]havepreviouslyreportedno

relationshipbetweenbiofilmformationandthe

r,

patientswhohadpreviouslyreceivedaminogly-

cosideswereatanincreadriskofbeingcolon-

idorinfectedbybiofinii.

Previousaminoglycosideumayexertadiffer-

entlectionpressureonbiofilmformation,irre-

spectiveofthein-vitrosusceptibility.

Insummary,>60%nii

isolatesfromclinicalsamplesformedbiofilm,and

theisolateswereassociatedmainlywith

solateswere

lessfrequentlyresistanttoimipenemand

ciprofloxacin.

ACKNOWLEDGEMENTS

Theresultsofthisstudywereprented,inpart,atthe16th

EuropeanCongressofClinicalMicrobiologyandInfectious

Dias(Nice,France).Thestudywassupportedbythe

MinisteriodeSanidadyConsumo,InstitutodeSaludCar-

losIII,andtheSpanishNetworkfortheRearchinInfectious

Dias(REIPIRD06⁄0008).Theauthorsthankthemembers

oftheSpanishGroupforNosocomialInfections(GEIH)ofthe

SpanishSocietyofInfectiousDiasandClinicalMicrobiol-

ogy(SEIMC),whocontributedtothisstudy,andwhohave

beenacknowledgedindetailelwhere[2].Theauthors

declarethattheyhavenoconflictsofinteresttodiscloin

relationtothiswork.

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Ó2008TheAuthors

JournalCompilationÓ2008EuropeanSocietyofClinicalMicrobiologyandInfectiousDias